The present embodiments relate generally to the field of additive manufacturing and, more particularly, to pre-treatment of powders used in additive manufacturing processes, such as with the use of fluidized beds.
Various additive manufacturing processes, as well as traditional powder processing and consolidation methods, rely on flowability of powders for proper application. Flowability of powders is a function of both powder size and shape. As powder size decreases, powder feeding becomes more difficult. Furthermore, powders with jagged or sharp shapes tend to interlock, disrupting powder flow. Therefore, the preferred powder shape is spherical, as this powder shape results in improved powder flow and consequently improved consistency in an additive build.
Powders are manufactured in numerous ways. One such powder manufacturing method is atomization, which is common for metal powders. Atomization can include both water atomization and gas atomization. Water atomization is generally cost effective but produces generally jagged granular powders. Gas atomization may produce more spherical powders, but is a less cost effective means for manufacturing powders. Other powder manufacturing methods, such as rotary atomization and plasma rotating electrode process (PREP), are even more costly than gas atomization. Another powder manufacturing technique, common for glass and ceramic powders, involves crushing or grinding. A ground ceramic or glass powder typically will be very jagged in shape, making flow difficult.
One prior method used to morph jagged or sharp powders into more spherical shapes is known as plasma spheroidization. Plasma spheroidization involves directing powders through a plasma jet, with the high plasma heat acting to spheroidize some of the powders and the jet stream acting to prevent agglomeration or sintering of powders. However, plasma spheroidization is very costly and presents challenges in selecting proper processing parameters. Furthermore, the extreme heat of the plasma can influence alloying element concentrations in powders, often vaporizing, and thus removing, low melt point elements as well as altering concentrations of other elements.